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F150 loss of power up top

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  • F150 loss of power up top

    Hey guys, long time no see.
    I am working on a 2010 Yamah F150TJR. Motor has been kept up with filter changes etc. Only run ethanol free gas from the marina. It is on a 24' tri-toon.

    It just started "starving" for fuel at upper rpms. Under that it seems ok at first. When you run it at 3000 rpms for a while it seems ok. Then we give her the gun and she is good to go a 5000rpms for about 10-15 seconds, then it really starts to lose power, then comes back just a bit, but will never catch back up, then loses more power again "surging". If you throttle down to 2300/3000 rpms the issue goes back away.

    I put my fuel pressure gauge on the high pressure side and I am reading 45psi at key on, and just under 40psi with the motor idling. (I havent hung off the back of the boat with a test gauge at WOT)

    I put a test tank with a clear hose up to the motor. Motor is drawing fuel fine. I even put a low pressure electric fuel pump (5psi) in the line and hooked it up while running just to see if it was a low pressure issue and it still acts up. So by doing that I hope to have eliminated the boat fuel tank as well as low pressure fuel pumps.

    Dumped and checked all filters. No debris, no water. Pulled VST and filter doesnt look gummed up. VST tank is clean as a whistle.

    So I am puzzled. Is there a resistance reading that I should have for the high pressure pump? Do they ever fail intermittently like this? Should I put it back together and send the fuel injectors off?

    Thanks guys, Im pretty crafty with all this stuff and always take the path of least resistance until I find the culprit.

    Electronics Troubleshooting Guide

    Free Online Outboard Service Manual

  • #2
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    Lots of things to check for..

    1. air leak in the intake manifold or fuel rail (o-rings for the injectors might be bad)
    2. clogged injectors
    3. throttle position sensor or ISC problem
    4. bent throttle valve(s)
    5. low compression
    6. bad pressure regulator
    7. damaged/bent VST needle valve